I can't say that I blame Nadine Dorries, the Conservative MP for Mid Bedfordshire, for making a fair bit of her council house background (the daughter of a bus driver, she grew up on an estate in Liverpool). Faced with Cameron, Osborne and co, I would do exactly the same. Nevertheless, it's a narrative that sits somewhat oddly with her regular policy pronouncements. Truly, Dorries confounds me. On the face of it, she is a real person. She began her working life as a nurse at a Warrington hospital and later ran her own business; she has three children. Certainly, she has had more of a life outside Westminster than some of her colleagues. So why are her ideological diktats always so baffling?

I'm damned if I know. All I can tell you for sure is that Dorries likes to plough her own furrow and that, metaphorically speaking, she has left the vertiginous and air-conditioned cab of her (bright blue) 280 horsepower tractor only rarely since her election to Parliament in 2005. Feel free to holler and wave, to throw clods of earth at her windscreen, but it will do no good. Derision is grist to Dorries's mill, as anyone who remembers her campaign to discourage the TUC from banning high heels at work will recall (the TUC – surprise! – wanted to do no such thing). And so she rumbles on.

Last week, Dorries put forward a parliamentary bill proposing that schools teach sexual abstinence to girls aged 13 to 16. Society, she argues, is "saturated in sex" and teenagers need to be taught that it is as "cool" to say no as it is to know how to use a condom. "By the age of 18, some girls have been taught three times how to put a condom on a boy," she said. Three times. And what about those boys? Should they just sit quietly in a corner with their fruit and their Durex Extra Safe? Yes!

Responding on her blog to the "liberal elite" who accused her of sexual stereotyping, Dorries stuck to her guns. "It's girls who get pregnant," she wrote, "girls who lose their education." There followed a list of other things that happen to girls, a slightly hysterical list that ended with the statement that it is girls who are "targeted by paedophiles".

Let us not get sidetracked by examining the usefulness, or otherwise, of the word "no" when it comes to paedophiles. The point about Dorries's latest batty idea is that it comes to us as if from another age. It's not only her quaint view that males are marauding beasts and females desireless vessels who must fend them off. Nor is it her blithe ignorance of the facts (comprehensive sex education is proving effective in reducing teenage pregnancies, which are, according to the most recent statistics from the Office for National Statistics, at their lowest rate since the 1980s). No, it's her startling lack of awareness of what it is like to be young that truly amazes. Wasn't this woman once a teenager herself? Was her estate really in Liverpool or was it, in fact, in Toytown?

I thought, with a hot pinch of embarrassment, about my teenage years. My sex life did not start until I left home, but this wasn't remotely because I was a "good" girl. I lost my virginity with what I can only describe as a deep sense of relief as soon as possible after I arrived at university and would have shed the wretched thing far sooner – years sooner – if only I'd been able. The sad truth is that during my teenage years I simply could not bag a boyfriend (or, at least, not a sufficiently experienced one). A squareish girl in a coolish school, I was an untouchable. Between 1983 and 1987, I had approximately three boyfriends. The third of these – just my luck – was a born-again Christian whose views on abstinence would have made Dorries proud.

No doubt there are some girls who feel pressured into having sex before they are ready. But, as Dorries's critics have already pointed out, if this is so, it stands to reason that there are boys who find themselves in a similar position. Nevertheless, instinct tells me these cases, on both sides, form only a tiny minority. My contemporaries were all having sex because they wanted to. Their hormones raged; some of them were in relationships; sex is enjoyable. So long as no one became pregnant, or caught a disease, where was the harm in it? I envied them.

As it happens, my mother taught biology in a unit for pregnant schoolgirls. She was straightforward about sex, too straightforward sometimes. The word "erection" fell easily from her lips and she thought you pathetically childish if this made you laugh. What did she think about my island state? I expect she was pleased. But this wasn't connected to a fear that I, like her charges, would get pregnant (I would have been frog-marched to our GP before you could say Marvelon had I embarked on anything even approaching a sex life). It was more that she thought that sex complicated relationships in the young, made them too intense.

I suppose there is some truth in this. On the other hand, when you're young, everything is intense. My moods were like the Shetlands: squally, with only the odd flash of sunshine. And I bet she would rather have had me boyfriended up and happy than silent and binge-drinking. I was once so drunk I had to be taken to hospital in an ambulance. Has Dorries, I wonder, ever stopped to consider the fact that safe sex is less harmful to young women than cheap cider?

At my school, a clutch of girls became pregnant and left before they turned 16. Some of them may have come to regret this later. But the fact that they did not seek to have abortions was evidence enough for me that, at the time, this was something they'd chosen (that, and their proud smiles). In cases like theirs, this coy emphasis on the word "no" isn't just a distraction from the work of educating girls about the contraceptive choices available to them; it's an irrelevance. They know what they want, and they know how to get it, and we'd be better off working out ways to ensure that teenage pregnancy need not signal the end of their education or their working life.

A while ago, waiting for a bus in Sheffield, I bumped into a woman I'd been at school with, one of those who'd left to have a baby at 15. Thinking about it now, it's striking the way our encounter, awkward but sweet, refused to fit Dorries's doom-laden and ugly paradigms about good girls and bad girls, about poverty and wealth. We grinned at each other and, as we talked about our lives, I had a deep and abiding sense that, ultimately, each of us had ended up with exactly what she wanted.

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